1. Field of the Invention
The present invention relates generally to valves for use in fluid circuits of refrigeration systems and, more particularly, to a valve stem seal assembly or configuration that protects a quarter turn ball valve's O-ring seal from exposure to refrigerant.
2. Discussion
Quarter turn ball valves are commonly used in refrigeration circuits to direct the flow of refrigerant through the circuits or to retain the charge of refrigerant in the circuits while isolating a portion of the circuit to facilitate the repair and/or replacement of system components or to perform general system maintenance. A key component of quarter turn ball valves is the valve stem packing and seal assembly or configuration. The purposes of the valve stem seal configuration is to seal the passage through which the rotatable valve stem passes through the valve body and to provide a bearing for resisting the internal pressure load acting on the valve stem. Many existing ball valve designs use an O-ring seal as the primary valve stem seal. The O-ring is lubricated prior to assembly of the valve and facilitates turning of the valve stem between the open and closed positions. Use of the O-ring as the primary seal typically exposes it to the flow of refrigerant through the valve.
Refrigerants such as R22 and R502 have been the standard refrigerants used in the refrigeration and air-conditioning industry for many years. Use of these refrigerants, however, have been found to pose a threat to the ozone in the atmosphere and the Environmental Protection Agency (EPA) has mandated that they be phased out of use. As a result, the refrigeration industry has been experimenting with new, ozone compatible refrigerants. When exposed to the standard refrigerants of the past (R22 and R502), O-ring s have maintained their lubrication capability. Exposure to the new EPA-correct refrigerants and blends, however, has dried out the O-rings. That is, the new refrigerants and blends tend to wash away the lubricants on the O-rings. As a result, lubrication of the O-rings has not been maintained and it is believed that the exposure of the O-rings to the refrigerant may be destructive to the O-ring material itself which could cause leakage of the refrigerant through the O-rings.
It is, therefore, an object of the present invention to provide a valve stem seal configuration for quarter turn ball valves that isolates and protects the seal O-rings from contact with refrigerants flowing through the valve.
Another object of the invention is to protect the O-rings from axial forces that can cause them to wear prematurely.